Method for padding processing with sub-region partitions in video stream

ABSTRACT

A method, computer program, and computer system is provided for video coding. Coded syntax elements corresponding to wrap-around padding process are decoded. At least one coded current picture is reconstructed using wrap-around padding process. The syntax elements indicate an offset value for wrap-around processing; or left and right padding width information. A flag indicates whether syntax elements corresponding to wrap-around padding process is present in parameter set. A pixel position for motion compensated prediction in a reference picture is determined by interpreting the syntax elements corresponding to wrap-around padding process with a clipping process.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. Provisional PatentApplication No. 62/903,635, filed on Sep. 20, 2019, in the U.S. Patentand Trademark Office, which is incorporated herein by reference in itsentirety.

FIELD

This disclosure relates generally to field of data processing, and moreparticularly to video encoding and decoding.

BACKGROUND

Video coding and decoding using inter-picture prediction with motioncompensation has been known for decades. Uncompressed digital video canconsist of a series of pictures, each picture having a spatial dimensionof, for example, 1920×1080 luminance samples and associated chrominancesamples. The series of pictures can have a fixed or variable picturerate (informally also known as frame rate), of, for example 60 picturesper second or 60 Hz. Uncompressed video has significant bitraterequirements. For example, 1080p60 4:2:0 video at 8 bit per sample(1920×1080 luminance sample resolution at 60 Hz frame rate) requiresclose to 1.5 Gbit/s bandwidth. An hour of such video requires more than600 GByte of storage space.

One purpose of video coding and decoding can be the reduction ofredundancy in the input video signal, through compression. Compressioncan help reducing aforementioned bandwidth or storage spacerequirements, in some cases by two orders of magnitude or more. Bothlossless and lossy compression, as well as a combination thereof can beemployed. Lossless compression refers to techniques where an exact copyof the original signal can be reconstructed from the compressed originalsignal. When using lossy compression, the reconstructed signal may notbe identical to the original signal, but the distortion between originaland reconstructed signal is small enough to make the reconstructedsignal useful for the intended application. In the case of video, lossycompression is widely employed. The amount of distortion tolerateddepends on the application; for example, users of certain consumerstreaming applications may tolerate higher distortion than users oftelevision contribution applications. The compression ratio achievablecan reflect that: higher allowable/tolerable distortion can yield highercompression ratios.

A video encoder and decoder can utilize techniques from several broadcategories, including, for example, motion compensation, transform,quantization, and entropy coding, some of which will be introducedbelow.

The concept of dividing a coded video bitstream into packets fortransportation over packet networks has been in use for decades. Earlyon, video coding standards and technologies were in their majorityoptimized for bot-oriented transport, and defined bitstreams.Packetization occurred in system layer interfaces specified, forexample, in Real-time Transport Protocol (RTP) payload formats. With theadvent of Internet connectivity suitable for mass-use of video over theInternet, the video coding standards reflected that prominent use casethrough the conceptual differentiation of a video coding layer (VCL) anda network abstraction layer (NAL). NAL units were introduced in H.264 in2003, and have been retained in certain video coding standards andtechnologies since then with only slight modifications.

A NAL unit can, in many cases, be seen as the smallest entity on which adecoder can act upon without necessarily having decoded all precedingNAL units of a coded video sequence. Insofar, NAL units enable certainerror resilience technologies as well as certain bitstream manipulationtechniques, to include bitstream pruning, by Media Aware NetworkElements (MANEs) such as Selective Forwarding Units (SFUs) or MultipointControl Units (MCUs).

FIG. 1 depicts relevant parts of the syntax diagram of NAL unit headersin accordance with H.264 (101) and H.265 (102), in both cases withoutany of their respective extensions. In both cases, theforbidden_zero_bit is a zero bit used for start code emulationprevention in certain system layer environments. The nal_unit_typesyntax element refers to the type of data a NAL unit carries, which canbe, for example, one of certain slice types, parameter set types,Supplementary Enhancement Information (SEI) message, and so on. TheH.265 NAL unit header further comprises nuh_layer_id andnuh_temporal_id_plus1, which indicate the spatial/SNR and temporal layerof a coded picture to which the NAL unit belongs.

It can be observed that the NAL unit header includes only easilyparseable fixed length codewords, that do not have any parsingdependency to other data in the bitstream such as, for example, otherNAL unit headers, parameter sets, and so on. As NAL unit headers are thefirst octets in a NAL unit, MANEs can easily extract them, parse them,and act on them. Other high level syntax elements, for example slice ortile headers, in contrast, are less easily accessible to MANEs as theymay require keeping parameter set context and/or the processing ofvariable length or arithmetically coded codepoints.

It can further be observed that the NAL unit headers as shown in FIG. 1do not include information that can associate a NAL unit to a codedpicture that is composed of a plurality of NAL units (such as, forexample, comprising multiple tiles or slices, at least some of whichbeing packetized in individual NAL units).

Certain transport technologies such as RTP (RFC 3550), MPEG-systemstandards, ISO file formats, and so on, may include certain information,often in the form of timing information such as presentation time (incase of MPEG and ISO file format) or capture time (in case of RTP) thatcan be easily accessible by MANEs and can help associating theirrespective transport units with coded pictures. However, the semanticsof these information can differ from one transport/storage technology toanother, and may have no direct relationship with the picture structureused in the video coding. Accordingly, these information may be, atbest, heuristics and may also not be particularly well suited toidentify whether or not NAL units in a NAL unit stream belong to thesame coded picture

SUMMARY

Embodiments relate to a method, system, and computer readable medium forvideo coding. According to one aspect, a method for video coding isprovided. The method may include decoding coded syntax elementscorresponding to wrap-around padding process. At least one coded currentpicture is reconstructed using wrap-around padding process. The syntaxelements indicate an offset value for wrap-around processing; or leftand right padding width information.

According to another aspect, a computer system for video coding isprovided. The computer system may include one or more processors, one ormore computer-readable memories, one or more computer-readable tangiblestorage devices, and program instructions stored on at least one of theone or more storage devices for execution by at least one of the one ormore processors via at least one of the one or more memories, wherebythe computer system is capable of performing a method. The method mayinclude decoding coded syntax elements corresponding to wrap-aroundpadding process. At least one coded current picture is reconstructedusing wrap-around padding process. The syntax elements indicate anoffset value for wrap-around processing; or left and right padding widthinformation.

According to yet another aspect, a computer readable medium for videocoding is provided. The computer readable medium may include one or morecomputer-readable storage devices and program instructions stored on atleast one of the one or more tangible storage devices, the programinstructions executable by a processor. The program instructions areexecutable by a processor for performing a method that may accordinglyinclude decoding coded syntax elements corresponding to wrap-aroundpadding process. At least one coded current picture is reconstructedusing wrap-around padding process. The syntax elements indicate anoffset value for wrap-around processing; or left and right padding widthinformation.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages will become apparentfrom the following detailed description of illustrative embodiments,which is to be read in connection with the accompanying drawings. Thevarious features of the drawings are not to scale as the illustrationsare for clarity in facilitating the understanding of one skilled in theart in conjunction with the detailed description. In the drawings:

FIG. 1 is a schematic illustration of NAL Unit Headers in accordancewith H.264 and H.265;

FIG. 2 is a schematic illustration of a simplified block diagram of acommunication system in accordance with an embodiment;

FIG. 3 is a schematic illustration of a simplified block diagram of acommunication system in accordance with an embodiment;

FIG. 4 is a schematic illustration of a simplified block diagram of adecoder in accordance with an embodiment;

FIG. 5 is a schematic illustration of a simplified block diagram of anencoder in accordance with an embodiment;

FIG. 6 is a schematic illustration of syntax elements for offsetsignaling in accordance with an embodiment;

FIG. 7 is a schematic illustration of syntax elements for padding widthsignaling of an encoder in accordance with an embodiment;

FIG. 8 is a schematic illustration of a simplified block diagram ofpadding processing of each sub-region (tile or sub-picture) inaccordance with an embodiment;

FIG. 9 is a schematic illustration of syntax elements for padding offsetsignaling of each sub-picture in accordance with an embodiment;

FIG. 10 is a schematic illustration of syntax elements for unifiedpadding offset signaling of each sub-picture in accordance with anembodiment; and

FIG. 11 is a schematic illustration of a computer system in accordancewith an embodiment.

DETAILED DESCRIPTION

Detailed embodiments of the claimed structures and methods are disclosedherein; however, it can be understood that the disclosed embodiments aremerely illustrative of the claimed structures and methods that may beembodied in various forms. Those structures and methods may, however, beembodied in many different forms and should not be construed as limitedto the exemplary embodiments set forth herein. Rather, these exemplaryembodiments are provided so that this disclosure will be thorough andcomplete and will fully convey the scope to those skilled in the art. Inthe description, details of well-known features and techniques may beomitted to avoid unnecessarily obscuring the presented embodiments.

Embodiments relate generally to the field of data processing, and moreparticularly to video encoding and decoding. The following describedexemplary embodiments provide a system, method and computer program to,among other things, reconstruct a coded current picture using awrap-around padding process based on decoding coded syntax elements.Therefore, some embodiments have the capacity to improve the field ofcomputing by allowing for coding of syntax elements to be used in thereconstruction of a compressed image.

As previously described, one purpose of video coding and decoding can bethe reduction of redundancy in the input video signal, throughcompression. Compression can help reducing aforementioned bandwidth orstorage space requirements, in some cases by two orders of magnitude ormore. Both lossless and lossy compression, as well as a combinationthereof can be employed. Lossless compression refers to techniques wherean exact copy of the original signal can be reconstructed from thecompressed original signal. When using lossy compression, thereconstructed signal may not be identical to the original signal, butthe distortion between original and reconstructed signal is small enoughto make the reconstructed signal useful for the intended application. Inthe case of video, lossy compression is widely employed. The amount ofdistortion tolerated depends on the application; for example, users ofcertain consumer streaming applications may tolerate higher distortionthan users of television contribution applications. The compressionratio achievable can reflect that: higher allowable/tolerable distortioncan yield higher compression ratios. However, when a picture ispartitioned into one or more sub-regions (tile, slice or sub-picture),boundary processing of each sub-region may affect the coding efficiencyand the subjective visual quality. Adaptive control of boundaryprocessing at each sub-region boundary is a key factor in 360 mediaprocessing. It may be advantageous, therefore, to reconstruct a codedcurrent picture using a wrap-around padding process based on decodingcoded syntax elements.

Aspects are described herein with reference to flowchart illustrationsand/or block diagrams of methods, apparatus (systems), and computerreadable media according to the various embodiments. It will beunderstood that each block of the flowchart illustrations and/or blockdiagrams, and combinations of blocks in the flowchart illustrationsand/or block diagrams, can be implemented by computer readable programinstructions.

The following described exemplary embodiments provide a system, methodand computer program that reconstructs a coded current picture using awrap-around padding process based on decoding coded syntax elements.

FIG. 2 illustrates a simplified block diagram of a communication system(200) according to an embodiment of the present disclosure. The system(200) may include at least two terminals (210-220) interconnected via anetwork (250). For unidirectional transmission of data, a first terminal(210) may code video data at a local location for transmission to theother terminal (220) via the network (250). The second terminal (220)may receive the coded video data of the other terminal from the network(250), decode the coded data and display the recovered video data.Unidirectional data transmission may be common in media servingapplications and the like.

FIG. 2 illustrates a second pair of terminals (230, 240) provided tosupport bidirectional transmission of coded video that may occur, forexample, during videoconferencing. For bidirectional transmission ofdata, each terminal (230, 240) may code video data captured at a locallocation for transmission to the other terminal via the network (250).Each terminal (230, 240) also may receive the coded video datatransmitted by the other terminal, may decode the coded data and maydisplay the recovered video data at a local display device.

In FIG. 2, the terminals (210-240) may be illustrated as servers,personal computers and smart phones but the principles of the presentdisclosure may be not so limited. Embodiments of the present disclosurefind application with laptop computers, tablet computers, media playersand/or dedicated video conferencing equipment. The network (250)represents any number of networks that convey coded video data among theterminals (210-240), including for example wireline and/or wirelesscommunication networks. The communication network (250) may exchangedata in circuit-switched and/or packet-switched channels. Representativenetworks include telecommunications networks, local area networks, widearea networks and/or the Internet. For the purposes of the presentdiscussion, the architecture and topology of the network (250) may beimmaterial to the operation of the present disclosure unless explainedherein below.

FIG. 3 illustrates, as an example for an application for the disclosedsubject matter, the placement of a video encoder and decoder in astreaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem (313), that caninclude a video source (301), for example a digital camera, creating afor example uncompressed video sample stream (302). That sample stream(302), depicted as a bold line to emphasize a high data volume whencompared to encoded video bitstreams, can be processed by an encoder(303) coupled to the camera (301). The encoder (303) can includehardware, software, or a combination thereof to enable or implementaspects of the disclosed subject matter as described in more detailbelow. The encoded video bitstream (304), depicted as a thin line toemphasize the lower data volume when compared to the sample stream, canbe stored on a streaming server (305) for future use. One or morestreaming clients (306, 308) can access the streaming server (305) toretrieve copies (307, 309) of the encoded video bitstream (304). Aclient (306) can include a video decoder (310) which decodes theincoming copy of the encoded video bitstream (307) and creates anoutgoing video sample stream (311) that can be rendered on a display(312) or other rendering device (not depicted). In some streamingsystems, the video bitstreams (304, 307, 309) can be encoded accordingto certain video coding/compression standards. Examples of thosestandards include ITU-T Recommendation H.265. Under development is avideo coding standard informally known as Versatile Video Coding or VVC.The disclosed subject matter may be used in the context of VVC.

FIG. 4 may be a functional block diagram of a video decoder (310)according to an embodiment of the present disclosure.

A receiver (410) may receive one or more codec video sequences to bedecoded by the decoder (310); in the same or another embodiment, onecoded video sequence at a time, where the decoding of each coded videosequence is independent from other coded video sequences. The codedvideo sequence may be received from a channel (412), which may be ahardware/software link to a storage device which stores the encodedvideo data. The receiver (410) may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver (410) may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory (415) may be coupled inbetween receiver (410) and entropy decoder/parser (420) (“parser”henceforth). When receiver (410) is receiving data from a store/forwarddevice of sufficient bandwidth and controllability, or from anisosychronous network, the buffer (415) may not be needed, or can besmall. For use on best effort packet networks such as the Internet, thebuffer (415) may be required, can be comparatively large and canadvantageously of adaptive size.

The video decoder (310) may include an parser (420) to reconstructsymbols (421) from the entropy coded video sequence. Categories of thosesymbols include information used to manage operation of the decoder(310), and potentially information to control a rendering device such asa display (312) that is not an integral part of the decoder but can becoupled to it, as was shown in FIG. 3. The control information for therendering device(s) may be in the form of Supplementary EnhancementInformation (SEI messages) or Video Usability Information (VUI)parameter set fragments (not depicted). The parser (420) mayparse/entropy-decode the coded video sequence received. The coding ofthe coded video sequence can be in accordance with a video codingtechnology or standard, and can follow principles well known to a personskilled in the art, including variable length coding, Huffman coding,arithmetic coding with or without context sensitivity, and so forth. Theparser (420) may extract from the coded video sequence, a set ofsubgroup parameters for at least one of the subgroups of pixels in thevideo decoder, based upon at least one parameter corresponding to thegroup. Subgroups can include Groups of Pictures (GOPs), pictures, tiles,slices, macroblocks, Coding Units (CUs), blocks, Transform Units (TUs),Prediction Units (PUs) and so forth. The entropy decoder/parser may alsoextract from the coded video sequence information such as transformcoefficients, quantizer parameter values, motion vectors, and so forth.

The parser (420) may perform entropy decoding/parsing operation on thevideo sequence received from the buffer (415), so to create symbols(421).

Reconstruction of the symbols (421) can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser (420). The flow of such subgroup control information between theparser (420) and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, decoder 310 can beconceptually subdivided into a number of functional units as describedbelow. In a practical implementation operating under commercialconstraints, many of these units interact closely with each other andcan, at least partly, be integrated into each other. However, for thepurpose of describing the disclosed subject matter, the conceptualsubdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit (451). Thescaler/inverse transform unit (451) receives quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc. as symbol(s) (421) from the parser (420). It can output blockscomprising sample values, that can be input into aggregator (455).

In some cases, the output samples of the scaler/inverse transform (451)can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit (452). In some cases, the intra pictureprediction unit (452) generates a block of the same size and shape ofthe block under reconstruction, using surrounding already reconstructedinformation fetched from the current (partly reconstructed) picture(456). The aggregator (455), in some cases, adds, on a per sample basis,the prediction information the intra prediction unit (452) has generatedto the output sample information as provided by the scaler/inversetransform unit (451).

In other cases, the output samples of the scaler/inverse transform unit(451) can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a Motion Compensation Prediction unit (453) canaccess reference picture memory (457) to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols (421) pertaining to the block, these samples can beadded by the aggregator (455) to the output of the scaler/inversetransform unit (in this case called the residual samples or residualsignal) so to generate output sample information. The addresses withinthe reference picture memory form where the motion compensation unitfetches prediction samples can be controlled by motion vectors,available to the motion compensation unit in the form of symbols (421)that can have, for example X, Y, and reference picture components.Motion compensation also can include interpolation of sample values asfetched from the reference picture memory when sub-sample exact motionvectors are in use, motion vector prediction mechanisms, and so forth.

The output samples of the aggregator (455) can be subject to variousloop filtering techniques in the loop filter unit (456). Videocompression technologies can include in-loop filter technologies thatare controlled by parameters included in the coded video bitstream andmade available to the loop filter unit (456) as symbols (421) from theparser (420), but can also be responsive to meta-information obtainedduring the decoding of previous (in decoding order) parts of the codedpicture or coded video sequence, as well as responsive to previouslyreconstructed and loop-filtered sample values.

The output of the loop filter unit (456) can be a sample stream that canbe output to the render device (312) as well as stored in the referencepicture memory (456) for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. Once a coded picture is fullyreconstructed and the coded picture has been identified as a referencepicture (by, for example, parser (420)), the current reference picture(456) can become part of the reference picture buffer (457), and a freshcurrent picture memory can be reallocated before commencing thereconstruction of the following coded picture.

The video decoder 420 may perform decoding operations according to apredetermined video compression technology that may be documented in astandard, such as ITU-T Rec. H.265. The coded video sequence may conformto a syntax specified by the video compression technology or standardbeing used, in the sense that it adheres to the syntax of the videocompression technology or standard, as specified in the videocompression technology document or standard and specifically in theprofiles document therein. Also necessary for compliance can be that thecomplexity of the coded video sequence is within bounds as defined bythe level of the video compression technology or standard. In somecases, levels restrict the maximum picture size, maximum frame rate,maximum reconstruction sample rate (measured in, for example megasamplesper second), maximum reference picture size, and so on. Limits set bylevels can, in some cases, be further restricted through HypotheticalReference Decoder (HRD) specifications and metadata for HRD buffermanagement signaled in the coded video sequence.

In an embodiment, the receiver (410) may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder (420) to properly decode the data and/or to moreaccurately reconstruct the original video data. Additional data can bein the form of, for example, temporal, spatial, or SNR enhancementlayers, redundant slices, redundant pictures, forward error correctioncodes, and so on.

FIG. 5 may be a functional block diagram of a video encoder (303)according to an embodiment of the present disclosure.

The encoder (303) may receive video samples from a video source (301)(that is not part of the encoder) that may capture video image(s) to becoded by the encoder (303).

The video source (301) may provide the source video sequence to be codedby the encoder (303) in the form of a digital video sample stream thatcan be of any suitable bit depth (for example: 8 bit, 10 bit, 12 bit, .. . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . ) and anysuitable sampling structure (for example Y CrCb 4:2:0, Y CrCb 4:4:4). Ina media serving system, the video source (301) may be a storage devicestoring previously prepared video. In a videoconferencing system, thevideo source (303) may be a camera that captures local image informationas a video sequence. Video data may be provided as a plurality ofindividual pictures that impart motion when viewed in sequence. Thepictures themselves may be organized as a spatial array of pixels,wherein each pixel can comprise one or more sample depending on thesampling structure, color space, etc. in use. A person skilled in theart can readily understand the relationship between pixels and samples.The description below focusses on samples.

According to an embodiment, the encoder (303) may code and compress thepictures of the source video sequence into a coded video sequence (543)in real time or under any other time constraints as required by theapplication. Enforcing appropriate coding speed is one function ofController (550). Controller controls other functional units asdescribed below and is functionally coupled to these units. The couplingis not depicted for clarity. Parameters set by controller can includerate control related parameters (picture skip, quantizer, lambda valueof rate-distortion optimization techniques, . . . ), picture size, groupof pictures (GOP) layout, maximum motion vector search range, and soforth. A person skilled in the art can readily identify other functionsof controller (550) as they may pertain to video encoder (303) optimizedfor a certain system design.

Some video encoders operate in what a person skilled in the are readilyrecognizes as a “coding loop”. As an oversimplified description, acoding loop can consist of the encoding part of an encoder (530)(“source coder” henceforth) (responsible for creating symbols based onan input picture to be coded, and a reference picture(s)), and a (local)decoder (533) embedded in the encoder (303) that reconstructs thesymbols to create the sample data a (remote) decoder also would create(as any compression between symbols and coded video bitstream islossless in the video compression technologies considered in thedisclosed subject matter). That reconstructed sample stream is input tothe reference picture memory (534). As the decoding of a symbol streamleads to bit-exact results independent of decoder location (local orremote), the reference picture buffer content is also bit exact betweenlocal encoder and remote encoder. In other words, the prediction part ofan encoder “sees” as reference picture samples exactly the same samplevalues as a decoder would “see” when using prediction during decoding.This fundamental principle of reference picture synchronicity (andresulting drift, if synchronicity cannot be maintained, for examplebecause of channel errors) is well known to a person skilled in the art.

The operation of the “local” decoder (533) can be the same as of a“remote” decoder (310), which has already been described in detail abovein conjunction with FIG. 4. Briefly referring also to FIG. 4, however,as symbols are available and en/decoding of symbols to a coded videosequence by entropy coder (545) and parser (420) can be lossless, theentropy decoding parts of decoder (310), including channel (412),receiver (410), buffer (415), and parser (420) may not be fullyimplemented in local decoder (533).

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. For this reason, thedisclosed subject matter focusses on decoder operation. The descriptionof encoder technologies can be abbreviated as they are the inverse ofthe comprehensively described decoder technologies. Only in certainareas a more detail description is required and provided below.

As part of its operation, the source coder (530) may perform motioncompensated predictive coding, which codes an input frame predictivelywith reference to one or more previously-coded frames from the videosequence that were designated as “reference frames.” In this manner, thecoding engine (532) codes differences between pixel blocks of an inputframe and pixel blocks of reference frame(s) that may be selected asprediction reference(s) to the input frame.

The local video decoder (533) may decode coded video data of frames thatmay be designated as reference frames, based on symbols created by thesource coder (530). Operations of the coding engine (532) mayadvantageously be lossy processes. When the coded video data may bedecoded at a video decoder (not shown in FIG. 5), the reconstructedvideo sequence typically may be a replica of the source video sequencewith some errors. The local video decoder (533) replicates decodingprocesses that may be performed by the video decoder on reference framesand may cause reconstructed reference frames to be stored in thereference picture cache (534). In this manner, the encoder (303) maystore copies of reconstructed reference frames locally that have commoncontent as the reconstructed reference frames that will be obtained by afar-end video decoder (absent transmission errors).

The predictor (535) may perform prediction searches for the codingengine (532). That is, for a new frame to be coded, the predictor (535)may search the reference picture memory (534) for sample data (ascandidate reference pixel blocks) or certain metadata such as referencepicture motion vectors, block shapes, and so on, that may serve as anappropriate prediction reference for the new pictures. The predictor(535) may operate on a sample block-by-pixel block basis to findappropriate prediction references. In some cases, as determined bysearch results obtained by the predictor (535), an input picture mayhave prediction references drawn from multiple reference pictures storedin the reference picture memory (534).

The controller (550) may manage coding operations of the video coder(530), including, for example, setting of parameters and subgroupparameters used for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder (545). The entropy coder translatesthe symbols as generated by the various functional units into a codedvideo sequence, by loss-less compressing the symbols according totechnologies known to a person skilled in the art as, for exampleHuffman coding, variable length coding, arithmetic coding, and so forth.

The transmitter (540) may buffer the coded video sequence(s) as createdby the entropy coder (545) to prepare it for transmission via acommunication channel (560), which may be a hardware/software link to astorage device which would store the encoded video data. The transmitter(540) may merge coded video data from the video coder (530) with otherdata to be transmitted, for example, coded audio data and/or ancillarydata streams (sources not shown).

The controller (550) may manage operation of the encoder (303). Duringcoding, the controller (550) may assign to each coded picture a certaincoded picture type, which may affect the coding techniques that may beapplied to the respective picture. For example, pictures often may beassigned as one of the following frame types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other frame in the sequence as a source of prediction.Some video codecs allow for different types of Intra pictures,including, for example Independent Decoder Refresh Pictures. A personskilled in the art is aware of those variants of I pictures and theirrespective applications and features.

A Predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A Bi-directionally Predictive Picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded non-predictively,via spatial prediction or via temporal prediction with reference to onepreviously coded reference pictures. Blocks of B pictures may be codednon-predictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video coder (303) may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video coder (303) may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter (540) may transmit additional datawith the encoded video. The video coder (530) may include such data aspart of the coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, Supplementary EnhancementInformation (SEI) messages, Visual Usability Information (VUI) parameterset fragments, and so on.

In an embodiment, 360 video is captured by a set of cameras or a cameradevice with multiple lenses. The cameras typically cover omni-directionsaround the centre point of the camera set. The images of the same timeinstance are stitched, possibly rotated, projected, and mapped onto apicture. The packed pictures are encoded as coded to a coded videobitstream, and streamed, according to a particular media container fileformat. The file includes metadata such as projection and packinginformation.

In an embodiment, 360 video may be projected to 2D video, usingequirectangular projection (ERP). The ERP projection may result in seamartifacts. The padded ERP (PERP) format may effectively reduce the seamartifacts in reconstructed viewports that encompass the left and rightboundaries of the ERP picture. However, padding and blending may not besufficient to completely resolve the seam issue.

In an embodiment, a horizontal geometry padding may be applied for ERPor PERP to reduce seam artifact. The padding process for PERP may be thesame as for ERP, with the exception that the offset may be based on theunpadded ERP width instead of the picture width to account for the sizeof the padded regions. If a reference block is outside the left (right)reference picture boundary, it may be replaced with the “wrapped-around”reference block shifted to the right (left) by the ERP width. Thetraditional repetitive padding may be employed in the verticaldirection. The blending of the left and right padded regions is kept outof loop, as a post-processing operation.

In an embodiment, a syntax to enable horizontal geometry padding ofreference pictures for the ERP and PERP formats is shown in FIG. 6.

sps_ref_wraparound_enabled_flag (602) equal to 1 specifies thathorizontal wrap-around motion compensation is used for inter prediction.sps_ref_wraparound_enabled_flag equal to 0 specifies that this motioncompensation method is not applied.

ref_wraparound_offset (603) specifies the offset in luma samples usedfor computing the horizontal wrap-around position. ref_wraparound_offsetshall be greater than pic_width_in_luma_samples−1, shall not be greaterthan pic_width_in_luma_samples, and shall be an integer multiple ofMinCbSizeY.

In an embodiment, syntax elements to enable horizontal geometry paddingof reference pictures for the ERP and PERP formats are shown in FIG. 7.

sps_ref_wraparound_enabled_flag (702) equal to 1 specifies thathorizontal wrap-around motion compensation is used for inter prediction.sps_ref_wraparound_enabled_flag equal to 0 specifies that this motioncompensation method is not applied.

left_wraparound_padding_width (703) specifies the width of left-sidepadding region in luma samples. ref_wraparound_offset shall be largerthan or equal to 0, shall not be larger thanpic_width_in_luma_samples/2, and shall be an integer multiple ofMinCbSizeY.

right_wraparound_padding_width (704) specifies the width of right-sidepadding region in luma samples. ref_wraparound_offset shall be largerthan or equal to 0, shall not be larger thanpic_width_in_luma_samples/2, and shall be an integer multiple ofMinCbSizeY.

Referring now to FIG. 8, an operational flowchart illustrating the stepsof a method 900 for encoding video data is depicted.

At 901, the method 900 includes parsing a parameter set.

At 902, the method 900 includes decoding picture partitioninginformation.

At 903, the method 900 includes determining whether padding is appliedto the boundaries of sub-regions.

At 904, the method 900 includes parsing the padding type if padding isapplied to the boundaries of sub-regions.

At 905, the method 900 includes decoding each sub-region without paddingif padding is not applied to the boundaries of sub-regions.

At 906, the method 900 includes determining whether wrap-around paddingis applied.

At 907, the method 900 includes padding the boundaries of sub-regionswith wrap-around padding if wrap-around padding is applied.

At 908, the method 900 includes padding the boundaries of sub-regionswith non-wrap-around padding if wrap-around padding is not applied.

In an embodiment, the wrap-around offset value may be obtained by thefollowing derivation process:

if ref_wraparound_offset is present  wrapAroundOffset =ref_wraparound_offset  else if left_wraparound_padding_width andright_wraparound_padding_width are present   wrapAroundOffset =pic_width_in_luma_samples − ( left_wraparound_padding_width +right_wraparound_padding_width )  else   wrapAroundOffset =pic_width_in_luma_samples

In an embodiment, to enable horizontal geometry padding of referencepictures for the ERP and PERP formats, the luma and chroma sampleinterpolation processes may be modified.

${Clip3\left( {x,y,z} \right)} = \left\{ {{\begin{matrix}{x;} & {z < x} \\{y;} & {z > y} \\{z;} & {otherwise}\end{matrix}{{ClipH}\left( {o,W,x} \right)}} = \left\{ \begin{matrix}{{\left( {o - {\left( {- x} \right)\%\mspace{20mu} o}} \right)\%\mspace{14mu} o};} & {x < 0} \\{{{\left( {x - W} \right)\%\mspace{14mu} o} + W - o};} & {x > {P - 1}} \\{x;} & {otherwise}\end{matrix} \right.} \right.$

Luma sample interpolation process. Inputs to this process may include aluma location in full-sample units (xInt_(L), yInt_(L)), a luma locationin fractional-sample units (xFrac_(L), yFrac_(L)), and the lumareference sample array refPicLX_(L). Outputs of this process may includea predicted luma sample value predSampleLX_(L).

The variables shift1, shift2 and shift3 are derived as follows. Thevariable shift1 is set equal to Min(4, BitDepth_(Y)−8), the variableshift2 is set equal to 6 and the variable shift3 is set equal to Max(2,14−BitDepth_(Y)). The variable picW is set equal topic_width_in_luma_samples and the variable picH is set equal topic_height_in_luma_samples. The variable xOffset is set equal towrapAroundOffset. The luma interpolation filter coefficients f_(L)[p]for each 1/16 fractional sample position p equal to xFrac_(L) oryFrac_(L) may be specified.

The predicted luma sample value predSampleLX_(L) is derived as follows.If both xFrac_(L) and yFrac_(L) are equal to 0, the following applies.If sps_ref_wraparound_enabled_flag is equal to 0, the value ofpredSampleLX_(L) is derived as predSampleLX_(L)=refPicLX_(L)[Clip3(0,picW−1, xInt_(L))][Clip3(0, picH−1, yInt_(L))]<<shift3. Otherwise, thevalue of predSampleLX_(L) is derived as:predSampleLX_(L)=refPicLX_(L)[ClipH(xOffset, picW, xInt_(L))][Clip3(0,picH−1, yInt_(L))]<<shift3. Otherwise if xFrac_(L) is not equal to 0 andyFrac_(L) is equal to 0, the following applies. The value of yPos_(L) isderived as yPos_(L)=Clip3(0, picH−1, yInt_(L)).

If sps_ref_wraparound_enabled_flag is equal to 0, the value ofpredSampleLX_(L) is derived as follows:predSampleLX _(L)=(f _(L)[xFrac_(L)][0]*refPicLX_(L)[Clip3(0,picW−1,xInt_(L)−3)][yPos_(L)]+f _(L)[xFrac_(L)][1]*refPicLX_(L)[Clip3(0,picW−1,xInt_(L)−2)][yPos_(L)]+f _(L)[xFrac_(L)][2]*refPicLX_(L)[Clip3(0,picW−1,xInt_(L)−1)][yPos_(L)]+f _(L)[xFrac_(L)][3]*refPicLX_(L)[Clip3(0,picW−1,xInt_(L))][yPos_(L)]+f _(L)[xFrac_(L)][4]*refPicLX_(L)[Clip3(0,picW−1,xInt_(L)+1)][yPos_(L)]+f _(L)[xFrac_(L)][5]*refPicLX_(L)[Clip3(0,picW−1,xInt_(L)+2)][yPos_(L)]+f _(L)[xFrac_(L)][6]*refPicLX_(L)[Clip3(0,picW−1,xInt_(L)+3)][yPos_(L)]+f _(L)[xFrac_(L)][7]*refPicLX_(L)[Clip3(0,picW−1,xInt_(L)+4)][yPos_(L)])>>shift1

Otherwise, the value of predSampleLX_(L) is derived as follows:predSampleLX _(L)=(f _(L)[xFrac_(L)][0]*refPicLX_(L)[ClipH(xOffset,picW,xInt_(L)−3)][yPos_(L)]+f_(L)[xFrac_(L)][1]*refPicLX_(L)[ClipH(xOffset,picW,xInt_(L)−2)][yPos_(L)]+f_(L)[xFrac_(L)][2]*refPicLX_(L)[ClipH(xOffset,picW,xInt_(L)−1)][yPos_(L)]+f_(L)[xFrac_(L)][3]*refPicLX_(L)[ClipH(xOffset,picW,xInt_(L))][yPos_(L)]+f_(L)[xFrac_(L)][4]*refPicLX_(L)[ClipH(xOffset,picW,xInt_(L)+1)][yPos_(L)]+f_(L)[xFrac_(L)][5]*refPicLX_(L)[ClipH(xOffset,picW,xInt_(L)+2)][yPos_(L)]+f_(L)[xFrac_(L)][6]*refPicLX_(L)[ClipH(xOffset,picW,xInt_(L)+3)][yPos_(L)]+f_(L)[xFrac_(L)][7]*refPicLX_(L)[ClipH(xOffset,picW,xInt_(L)+4)][yPos_(L)])>>shift.

Otherwise if xFrac_(L) is equal to 0 and yFrac_(L) is not equal to 0,the value of predSampleLX_(L) is derived as follows. Ifsps_ref_wraparound_enabled_flag is equal to 0, the value of xPos_(L) isderived as xPos_(L)=Clip3(0, picW−1, xInt_(L)). Otherwise, the value ofxPos_(L) is derived as: xPos_(L)=ClipH(xOffset, picW, xInt_(L)).

The predicted luma sample value predSampleLX_(L) is derived as follows:predSampleLX _(L)=(f _(L)[yFrac_(L)][0]*refPicLX_(L)[xPos_(L)][Clip3(0,picH−1,yInt_(L)−3)]+f _(L)[yFrac_(L)][1]*refPicLX_(L)[xPos_(L)][Clip3(0,picH−1,yInt_(L)−2)]+f _(L)[yFrac_(L)][2]*refPicLX_(L)[xPos_(L)][Clip3(0,picH−1,yInt_(L)−1)]+f _(L)[yFrac_(L)][3]*refPicLX_(L)[xPos_(L)][Clip3(0,picH−1,yInt_(L))]+f _(L)[yFrac_(L)][4]*refPicLX_(L)[xPos_(L)][Clip3(0,picH−1,yInt_(L)+1)]+f _(L)[yFrac_(L)][5]*refPicLX_(L)[xPos_(L)][Clip3(0,picH−1,yInt_(L)+2)]+f _(L)[yFrac_(L)][6]*refPicLX_(L)[xPos_(L)][Clip3(0,picH−1,yInt_(L)+3)]+f _(L)[yFrac_(L)][7]*refPicLX_(L)[xPos_(L)][Clip3(0,picH−1,yInt_(L)+4)])>>shift1.

Otherwise if xFrac_(L) is not equal to 0 and yFrac_(L) is not equal to0, the value of predSampleLX_(L) is derived as follows. Ifsps_ref_wraparound_enabled_flag is equal to 0, the sample array temp[n]with n=0 . . . 7, is derived as follows:yPos_(L)=Clip3(0,picH−1,yInt_(L) +n−3)temp[n]=(f _(L)[xFrac_(L)][0]*refPicLX_(L)[Clip3(0,picW−1,xInt_(L)−3)][yPos_(L)]+f _(L)[xFrac_(L)][1]*refPicLX_(L)[Clip3(0,picW−1,xInt_(L)−2)][yPos_(L)]+f _(L)[xFrac_(L)][2]*refPicLX_(L)[Clip3(0,picW−1,xInt_(L)−1)][yPos_(L)]+f _(L)[xFrac_(L)][3]*refPicLX_(L)[Clip3(0,picW−1,xInt_(L))][yPos_(L)]+f _(L)[xFrac_(L)][4]*refPicLX_(L)[Clip3(0,picW−1,xInt_(L)+1)][yPos_(L)]+f _(L)[xFrac_(L)][5]*refPicLX_(L)[Clip3(0,picW−1,xInt_(L)+2)][yPos_(L)]+f _(L)[xFrac_(L)][6]*refPicLX_(L)[Clip3(0,picW−1,xInt_(L)+3)][yPos_(L)]+f _(L)[xFrac_(L)][7]*refPicLX_(L)[Clip3(0,picW−1,xInt_(L)+4)][yPos_(L)])>>shift1.

Otherwise, the sample array temp[n] with n=0 . . . 7, is derived asfollows:yPos_(L)=Clip3(0,picH−1,yInt_(L) +n−3)temp[n]=(f _(L)[xFrac_(L)][0]*refPicLX_(L)[ClipH(xOffset,picW,xInt_(L)−3)][yPos_(L)]+f_(L)[xFrac_(L)][1]*refPicLX_(L)[ClipH(xOffset,picW,xInt_(L)−2)][yPos_(L)]+f_(L)[xFrac_(L)][2]*refPicLX_(L)[ClipH(xOffset,picW,xInt_(L)−1)][yPos_(L)]+f_(L)[xFrac_(L)][3]*refPicLX_(L)[ClipH(xOffset,picW,xInt_(L))][yPos_(L)]+f_(L)[xFrac_(L)][4]*refPicLX_(L)[ClipH(xOffset,picW,xInt_(L)+1)][yPos_(L)]+f_(L)[xFrac_(L)][5]*refPicLX_(L)[ClipH(xOffset,picW,xInt_(L)+2)][yPos_(L)]+f_(L)[xFrac_(L)][6]*refPicLX_(L)[ClipH(xOffset,picW,xInt_(L)+3)][yPos_(L)]+f_(L)[xFrac_(L)][7]*refPicLX_(L)[ClipH(xOffset,picW,xInt_(L)+4)][yPos_(L)])>>shift1.

The predicted luma sample value predSampleLX_(L) is derived as follows:predSampleLX _(L)=(f _(L)[yFrac_(L)][0]*temp[0]+f_(L)[yFrac_(L)][1]*temp[1]+f _(L)[yFrac_(L)][2]*temp[2]+f_(L)[yFrac_(L)][3]*temp[3]+f _(L)[yFrac_(L)][4]*temp[4]+f_(L)[yFrac_(L)][5]*temp[5]+f _(L)[yFrac_(L)][6]*temp[6]+f_(L)[yFrac_(L)][7]*temp[7])>>shift2.

Chroma sample interpolation process. Inputs to this process may includea chroma location in full-sample units (xInt_(C), yInt_(C)), a chromalocation in 1/32 fractional-sample units (xFrac_(C), yFrac_(C)), and thechroma reference sample array refPicLX_(C). Outputs of this process mayinclude a predicted chroma sample value predSampleLX_(C)

The variables shift1, shift2 and shift3 are derived as follows. Thevariable shift1 is set equal to Min(4, BitDepth_(C)−8), the variableshift2 is set equal to 6 and the variable shift3 is set equal to Max(2,14−BitDepth_(C)). The variable picW_(C) is set equal topic_width_in_luma_samples/SubWidthC and the variable picH_(C) is setequal to pic_height_in_luma_samples/SubHeightC. The variable xOffset_(C)is set equal to wrapAroundOffset/SubWidthC. The luma interpolationfilter coefficients f_(C)[p] for each 1/32 fractional sample position pequal to xFrac_(C) or yFrac_(C) may be specified.

The predicted chroma sample value predSampleLX_(C) is derived asfollows. If both xFrac_(C) and yFrac_(C) are equal to 0, the followingapplies. If sps_ref_wraparound_enabled_flag is equal to 0, the value ofpredSampleLX_(C) is derived as: predSampleLX_(C)=refPicLX_(C)[Clip3(0,picW_(C)−1, xInt_(C))][Clip3(0, picH_(C)−1, yInt_(C))]<<shift3.

Otherwise, the value of predSampleLX_(C) is derived aspredSampleLX_(C)=refPicLX_(C)[ClipH(xOffset_(C), picW_(C),xInt_(C))][Clip3(0, picH_(C)−1, yInt_(C))]<<shift3.−

Otherwise if xFrac_(C) is not equal to 0 and yFrac_(C) is equal to 0,the following applies. The value of yPos_(C) is derived asyPos_(C)=Clip3(0, picH_(C)−1, yInt_(C)). Ifsps_ref_wraparound_enabled_flag is equal to 0, the value ofpredSampleLX_(C) is derived as:predSampleLX _(C)=(f _(C)[xFrac_(C)][0]*refPicLX _(C)[Clip3(0,picW_(C)−1,xInt_(C)−1)][yInt_(C)]+f _(C)[xFrac_(C)][1]*refPicLX_(C)[Clip3(0,picW _(C)−1,xInt_(C))][yInt_(C)]+f_(C)[xFrac_(C)][2]*refPicLX _(C)[Clip3(0,picW_(C)−1,xInt_(C)+1)][yInt_(C)]+f _(C)[xFrac_(C)][3]*refPicLX_(C)[Clip3(0,picW _(C)−1,xInt_(C)+2)][yInt_(C)])>>shift1.

Otherwise, the value of predSampleLX_(C) is derived as:predSampleLX _(C)=(f _(C)[xFrac_(C)][0]*refPicLX_(C)[ClipH(xOffset_(C),picW _(C) ,xInt_(C)−1)][yPos_(C)]+f_(C)[xFrac_(C)][1]*refPicLX _(C)[ClipH(xOffset_(C),picW _(C),xInt_(C))][yPos_(C)]+f _(C)[xFrac_(C)][2]*refPicLX_(C)[ClipH(xOffset_(C),picW _(C) ,xInt_(C)+1)][yPos_(C)]+f_(C)[xFrac_(C)][3]*refPicLX _(C)[ClipH(xOffset_(C),picW _(C),xInt_(C)+2)][yPos_(C)])>>shift1.

Otherwise if xFrac_(C) is equal to 0 and yFrac_(C) is not equal to 0,the value of predSampleLX_(C) is derived as follows. Ifsps_ref_wraparound_enabled_flag is equal to 0, the value of xPos_(C) isderived as: xPos_(C)=Clip3(0, picW_(C)−1, xInt_(C)). Otherwise, thevalue of xPos_(C) is derived as: xPos_(C)=ClipH(xOffset_(C), picW_(C),xInt_(C))

The predicted chroma sample value predSampleLX_(C) is derived asfollows:predSampleLX _(C)=(f _(C)[yFrac_(C)][0]*refPicLX_(C)[xPos_(C)][Clip3(0,picH _(C)−1,yInt_(C)−1)]+f_(C)[yFrac_(C)][1]*refPicLX _(C)[xPos_(C)][Clip3(0,picH_(C)−1,yInt_(C))]+f _(C)[yFrac_(C)][2]*refPicLX_(C)[xPos_(C)][Clip3(0,picH _(C)−1,yInt_(C)+1)]+f_(C)[yFrac_(C)][3]*refPicLX _(C)[xPos_(C)][Clip3(0,picH_(C)−1,yInt_(C)+2)])>>shift1.

Otherwise if xFrac_(C) is not equal to 0 and yFrac_(C) is not equal to0, the value of predSampleLX_(C) is derived as follows. Ifsps_ref_wraparound_enabled_flag is equal to 0, the sample array temp[n]with n=0 . . . 3, is derived as follows:yPos_(C)=Clip3(0,picH _(C)−1,yInt_(C) +n−1)temp[n]=(f _(C)[xFrac_(C)][0]*refPicLX _(C)[Clip3(0,picW_(C)−1,xInt_(C)−1)][yPos_(C)]+f _(C)[xFrac_(C)][1]*refPicLX_(C)[Clip3(0,picW _(C)−1,xInt_(C))][yPos_(C)]+f_(C)[xFrac_(C)][2]*refPicLX _(C)[Clip3(0,picW_(C)−1,xInt_(C)+1)][yPos_(C)]+f _(C)[xFrac_(C)][3]*refPicLX_(C)[Clip3(0,picW _(C)−1,xInt_(C)+2)][yPos_(C)])>>shift1.

Otherwise, the sample array temp[n] with n=0 . . . 3, is derived asfollows:yPos_(C)=Clip3(0,picH _(C)−1,yInt_(C) +n−1)temp[n]=(f _(C)[xFrac_(C)][0]*refPicLX _(C)[ClipH(xOffset_(C),picW _(C),xInt_(C)−1)][yPos_(C)]+f _(C)[xFrac_(C)][1]*refPicLX_(C)[ClipH(xOffset_(C),picW _(C) ,xInt_(C))][yPos_(C)]+f_(C)[xFrac_(C)][2]*refPicLX _(C)[ClipH(xOffset_(C),picW _(C),xInt_(C)+1)][yPos_(C)]+f _(C)[xFrac_(C)][3]*refPicLX_(C)[ClipH(xOffset_(C),picW _(C) ,xInt_(C)+2)][yPos_(C)])>>shift1.

The predicted chroma sample value predSampleLX_(C) is derived asfollows:predSampleLX _(C)=(f _(C)[yFrac_(C)][0]*temp[0]+f_(C)[yFrac_(C)][1]*temp[1]+f _(C)[yFrac_(C)][2]*temp[2]+f_(C)[yFrac_(C)][3]*temp[3])>>shift2.

In an embodiment, if sps_ref_wraparound_enabled_flag is equal to 0 or isnot present, a traditional repetitive padding may be applied. Otherwise,the wrap-around padding may be applied.

In an embodiment, the wrap-around padding may be applied at bothhorizontal and vertical boundaries. A flag in a high level syntaxstructure may indicate the wrap-around padding is applied in bothhorizontal and vertical.

In an embodiment, the wrap-around padding may be applied at tile or tilegroup boundaries. A flag in a high level syntax structure may indicatethe wrap-around padding is applied in both horizontal and vertical.

In an embodiment, the reference picture may be identical to the currentpicture for motion compensated prediction. The wrap-around padding maybe applied at the boundary of the current picture, when the currentpicture is the reference.

In an embodiment, when a picture is partitioned into one or moresub-picture, which is a rectangular region of one or more slices, theboundary of each sub-picture may or may not be handled as a pictureboundary. Treating a sub-picture as a picture indicates that theboundary of each sub-picture may be padded for motion compensatedprediction.

Referring to FIG. 9, in SPS (or any other parameter set),subpic_treated_as_pic_flag[i] equal to 1 specifies that the i-thsubpicture of each coded picture in the CVS is treated as a picture inthe decoding process. subpic_treated_as_pic_flag[i] equal to 0 specifiesthat the i-th subpicture of each coded picture in the CVS is not treatedas a picture in the decoding process. When not present, the value ofsubpic_treated_as_pic_flag[i] is inferred to be equal to 0.

In the same embodiment, when subpic_treated_as_pic_flag[i] is equal to1, which indicates that the i-th sub-picture is treated as a picture, aflag subpic_ref_wraparound_enabled_flag[i] is signaled.subpic_ref_wraparound_enabled_flag[i] equal to 1.subpic_ref_wraparound_enabled_flag[i] equal to 1 specifies thathorizontal wrap-around motion compensation is applied in interprediction at the boundary of the i-th sub-picture of each codedpicture. sps_ref_wraparound_enabled_flag[i] equal to 0 specifies thathorizontal wrap-around motion compensation is not applied at theboundary of the i-th sub-picture of each coded picture.

In the same embodiment, subpic_ref_wraparound_offset_minus1[i] plus 1specifies the offset of the i-th sub-picture of each coded picture, usedfor computing the horizontal wrap-around position in units of MinCbSizeYluma samples.

In the same embodiment, the interploation filtering process is asfollows. Luma sample interpolation filtering process. Inputs to thisprocess may include a luma location in full-sample units (xInt_(L),yInt_(L)), a luma location in fractional-sample units (xFrac_(L),yFrac_(L)), a luma location in full-sample units (xSbInt_(L),ySbInt_(L)) specifying the top-left sample of the bounding block forreference sample padding relative to the top-left luma sample of thereference picture, the luma reference sample array refPicLX_(L), thehalf sample interpolation filter index hpelIfIdx, a variable sbWidthspecifying the width of the current subblock, a variable sbHeightspecifying the height of the current subblock, and a luma location (xSb,ySb) specifying the top-left sample of the current subblock relative tothe top-left luma sample of the current picture. Outputs of this processmay include a predicted luma sample value predSampleLX_(L)

The variables shift1, shift2 and shift3 are derived as follows. Thevariable shift1 is set equal to Min(4, BitDepth_(Y)−8), the variableshift2 is set equal to 6 and the variable shift3 is set equal to Max(2,14−BitDepth_(Y)). The variable picW is set equal topic_width_in_luma_samples and the variable picH is set equal topic_height_in_luma_samples.

The luma interpolation filter coefficients f_(L)[p] for each 1/16fractional sample position p equal to xFrac_(L) or yFrac_(L) are derivedas follows. If MotionModelIdc[xSb][ySb] is greater than 0, and sbWidthand sbHeight are both equal to 4, the luma interpolation filtercoefficients f_(L)[p] may be specified. Otherwise, the lumainterpolation filter coefficients f_(L)[p] are specified in Table 8-11depending on hpelIfIdx.

The luma locations in full-sample units (xInt_(i), yInt_(i)) are derivedas follows for i=0 . . . 7. If subpic_treated_as_pic_flag[SubPicIdx] isequal to 1, the following applies:xInt_(i)=Clip3(SubPicLeftBoundaryPos,SubPicRightBoundaryPos,subpic_ref_wraparound_enabled_flag[SubPicIdx]ClipH((subpic_ref_wraparound_offset_minus1[SubPicIdx]+1)*MinCbSizeY,SubPicRightBoundaryPos,xInt_(L) +i−3):xInt_(L) +i−3).yInt_(i)=Clip3(SubPicTopBoundaryPos,SubPicBotBoundaryPos,yInt_(L) +i−3).

Otherwise (subpic_treated_as_pic_flag[SubPicIdx] is equal to 0), thefollowing applies:xInt_(i)=Clip3(0,picW−1,sps_ref_wraparound_enabled_flagClipH((sps_ref_wraparound_offset_minus1+1)*MinCbSizeY,picW,xInt_(L)+i−3):xInt_(L) +i−3)yInt_(i)=Clip3(0,picH−1,yInt_(L) +i−3)

The luma locations in full-sample units are further modified as followsfor i=0 . . . 7:xInt_(i)=Clip3(xSbInt_(L)−3,xSbInt_(L) +sbWidth+4,xInt_(i))yInt_(i)=Clip3(ySbInt_(L)−3,ySbInt_(L) +sbHeight+4,yInt_(i))

The predicted luma sample value predSampleLX_(L) is derived as follows.If both xFrac_(L) and yFrac_(L) are equal to 0, the value ofpredSampleLX_(L) is derived as:

predSampleLX_(L)=refPicLX_(L)[xInt₃][yInt₃]<<shift3.

Otherwise, if xFrac_(L) is not equal to 0 and yFrac_(L) is equal to 0,the value of predSampleLX_(L) is derived as predSampleLX_(L)=(Σ_(i=0)⁷f_(L)[xFrac_(L)][i]*refPicLX _(L)[xInt_(i)][yInt₃])>>shift1.

Otherwise, if xFrac_(L) is equal to 0 and yFrac_(L) is not equal to 0,the value of predSampleLX_(L) is derived as predSampleLX_(L)=(Σ_(i=0)⁷f_(L)[yFrac_(L)][i]*refPicLX _(L)[xInt₃][yInt_(i)])>>shift1.

Otherwise, if xFrac_(L) is not equal to 0 and yFrac_(L) is not equal to0, the value of predSampleLX_(L) is derived as follows:

The sample array temp[n] with n=0 . . . 7, is derived as:temp[n]=(Σ_(i=0) ⁷f_(L)[xFrac_(L)][i]*refPicLX_(L)[xInt_(i)][yInt_(n)])>>shift1.

The predicted luma sample value predSampleLX_(L) is derived aspredSampleLX_(L)=(Σ_(i=0) ⁷f_(L)[yFrac_(L)][i]*temp[i])>>shift2.

In the same or another embodiment, referring to FIG. 10, in SPS (or anyother parameter set), all_subpic_treated_as_pic_flag equal to 1specifies that any sub-picture of each coded picture in the CVS istreated as a picture in the decoding process.subpic_treated_as_pic_flag[i] equal to 0 specifies that any subpictureof each coded picture in the CVS is not treated as a picture in thedecoding process.

In the same embodiment, when all_subpic_treated_as_pic_flag[i] is equalto 1, a flag all_subpic_ref_wraparound_enabled_flag is signaled.all_subpic_ref_wraparound_enabled_flag equal to 1 specifies thathorizontal wrap-around motion compensation is applied in interprediction at the boundary of any sub-picture of each coded picture.all_sps_ref_wraparound_enabled_flag equal to 0 specifies that horizontalwrap-around motion compensation is not applied at the boundary of anysub-picture of each coded picture.

In the same embodiment, all_subpic_ref_wraparound_offset_minus1[i] plus1 specifies the offset of any sub-picture of each coded picture, usedfor computing the horizontal wrap-around position in units of MinCbSizeYluma samples. In the same embodiment, when subpic_treated_as_pic_flag[i]is not present, the value of subpic_treated_as_pic_flag[i] is inferredto be equal to all_subpic_treated_as_pic_flag.

In the same embodiment, when subpic_ref_wraparound_enabled_flag[i] isnot present, the value of subpic_ref_wraparound_enabled_flag[i] isinferred to be equal to all_subpic_ref_wraparound_enabled_flag.

In the same embodiment, when subpic_ref_wraparound_offset_minus1[i] isnote present, the value of subpic_ref_wraparound_offset_minus1[i] isinferred to be equal to all_subpic_ref_wraparound_offset_minus1.

The techniques for wrap-around padding process described above, can beimplemented as computer software using computer-readable instructionsand physically stored in one or more computer-readable media. Forexample, FIG. 11 shows a computer system 800 suitable for implementingcertain embodiments of the disclosed subject matter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by computer central processing units (CPUs),Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 11 for computer system 800 are exemplary innature and are not intended to suggest any limitation as to the scope ofuse or functionality of the computer software implementing embodimentsof the present disclosure. Neither should the configuration ofcomponents be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system 800.

Computer system 800 may include certain human interface input devices.Such a human interface input device may be responsive to input by one ormore human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard 801, mouse 802, trackpad 803, touch screen 810,data-glove 804, joystick 805, microphone 806, scanner 807, camera 808.

Computer system 800 may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen 810, data-glove 804, or joystick 805, but there can also betactile feedback devices that do not serve as input devices), audiooutput devices (such as: speakers 809, headphones (not depicted)),visual output devices (such as screens 810 to include CRT screens, LCDscreens, plasma screens, OLED screens, each with or without touch-screeninput capability, each with or without tactile feedback capability—someof which may be capable to output two dimensional visual output or morethan three dimensional output through means such as stereographicoutput; virtual-reality glasses (not depicted), holographic displays andsmoke tanks (not depicted)), and printers (not depicted).

Computer system 800 can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW820 with CD/DVD or the like media 821, thumb-drive 822, removable harddrive or solid state drive 823, legacy magnetic media such as tape andfloppy disc (not depicted), specialized ROM/ASIC/PLD based devices suchas security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system 800 can also include interface to one or morecommunication networks. Networks can for example be wireless, wireline,optical. Networks can further be local, wide-area, metropolitan,vehicular and industrial, real-time, delay-tolerant, and so on. Examplesof networks include local area networks such as Ethernet, wireless LANs,cellular networks to include GSM, 3G, 4G, 5G, LTE and the like, TVwireline or wireless wide area digital networks to include cable TV,satellite TV, and terrestrial broadcast TV, vehicular and industrial toinclude CANBus, and so forth. Certain networks commonly require externalnetwork interface adapters that attached to certain general purpose dataports or peripheral buses (849) (such as, for example USB ports of thecomputer system 800; others are commonly integrated into the core of thecomputer system 800 by attachment to a system bus as described below(for example Ethernet interface into a PC computer system or cellularnetwork interface into a smartphone computer system). Using any of thesenetworks, computer system 800 can communicate with other entities. Suchcommunication can be uni-directional, receive only (for example,broadcast TV), uni-directional send-only (for example CANbus to certainCANbus devices), or bi-directional, for example to other computersystems using local or wide area digital networks. Certain protocols andprotocol stacks can be used on each of those networks and networkinterfaces as described above.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core 840 of thecomputer system 800.

The core 840 can include one or more Central Processing Units (CPU) 841,Graphics Processing Units (GPU) 842, specialized programmable processingunits in the form of Field Programmable Gate Areas (FPGA) 843, hardwareaccelerators for certain tasks 844, and so forth. These devices, alongwith Read-only memory (ROM) 845, Random-access memory 846, internal massstorage such as internal non-user accessible hard drives, SSDs, and thelike 847, may be connected through a system bus 848. In some computersystems, the system bus 848 can be accessible in the form of one or morephysical plugs to enable extensions by additional CPUs, GPU, and thelike. The peripheral devices can be attached either directly to thecore's system bus 848, or through a peripheral bus 849. Architecturesfor a peripheral bus include PCI, USB, and the like.

CPUs 841, GPUs 842, FPGAs 843, and accelerators 844 can execute certaininstructions that, in combination, can make up the aforementionedcomputer code. That computer code can be stored in ROM 845 or RAM 846.Transitional data can be also be stored in RAM 846, whereas permanentdata can be stored for example, in the internal mass storage 847. Faststorage and retrieve to any of the memory devices can be enabled throughthe use of cache memory, that can be closely associated with one or moreCPU 841, GPU 842, mass storage 847, ROM 845, RAM 846, and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture 800, and specifically the core 840 can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core 840 that are of non-transitorynature, such as core-internal mass storage 847 or ROM 845. The softwareimplementing various embodiments of the present disclosure can be storedin such devices and executed by core 840. A computer-readable medium caninclude one or more memory devices or chips, according to particularneeds. The software can cause the core 840 and specifically theprocessors therein (including CPU, GPU, FPGA, and the like) to executeparticular processes or particular parts of particular processesdescribed herein, including defining data structures stored in RAM 846and modifying such data structures according to the processes defined bythe software. In addition or as an alternative, the computer system canprovide functionality as a result of logic hardwired or otherwiseembodied in a circuit (for example: accelerator 844), which can operatein place of or together with software to execute particular processes orparticular parts of particular processes described herein. Reference tosoftware can encompass logic, and vice versa, where appropriate.Reference to a computer-readable media can encompass a circuit (such asan integrated circuit (IC)) storing software for execution, a circuitembodying logic for execution, or both, where appropriate. The presentdisclosure encompasses any suitable combination of hardware andsoftware.

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof.

What is claimed is:
 1. A method of video decoding, executable by aprocessor, the method comprising: decoding coded syntax elementscorresponding to a wrap-around padding process based on shifting areference block by a reference wrap-around padding width value that isdetermined based on locations of luma samples in the reference block;and reconstructing at least one coded current picture using thewrap-around padding process, wherein the wrap-around padding process isapplied at boundaries of subpictures.
 2. The method of claim 1, whereinthe decoded syntax elements indicate an offset value for wrap-aroundprocessing; or left and right padding width information.
 3. The methodof claim 2, wherein a flag indicates whether syntax elementscorresponding to the wrap-around padding process are present in aparameter set.
 4. The method of claim 3, wherein a pixel position for amotion compensated prediction in a reference picture is determined byinterpreting the syntax elements corresponding to the wrap-aroundpadding process with a clipping process.
 5. The method of claim 4,wherein a fractional pixel is interpolated for the motion compensatedprediction based on the determined pixel position.
 6. The method ofclaim 5, wherein an overwrapped region is blended to remove a seamartifact as a post processing.
 7. The method of claim 1, wherein thewrap-around padding process is applied at a tile or a tile groupboundary.
 8. The method of claim 1, wherein the at least one codedcurrent picture is a reference for motion compensation.
 9. The method ofclaim 8, wherein the wrap-around padding process is applied at aboundary of the at least one coded current picture.
 10. The method ofclaim 1, wherein the wrap-around padding process is applied at ahorizontal, a vertical boundary or at both the vertical and horizontalboundaries.
 11. The method of claim 10, wherein a flag in a high levelsyntax structure indicates whether the wrap-around padding process isapplied at the horizontal, the vertical boundary or both the verticaland horizontal boundaries.
 12. A computer system for video coding, thecomputer system comprising: one or more computer-readable non-transitorystorage media configured to store computer program code; and one or morecomputer processors configured to access said computer program code andoperate as instructed by said computer program code, said computerprogram code including: decoding code configured to cause the one ormore computer processors to decode coded syntax elements correspondingto a wrap-around padding process based on shifting a reference block bya reference wraparound padding width value that is determined based onlocations of luma samples in the reference block; and reconstructingcode configured to cause the one or more computer processors toreconstruct at least one coded current picture using the wrap-aroundpadding process, wherein the wrap-around padding process is applied atboundaries of subpictures.
 13. The computer system of claim 12, whereinthe decoded syntax elements indicate an offset value for wrap-aroundprocessing; or left and right padding width information.
 14. Thecomputer system of claim 13, wherein a flag indicates whether syntaxelements corresponding to the wrap-around padding process are present ina parameter set.
 15. The computer system of claim 14, wherein a pixelposition for a motion compensated prediction in a reference picture isdetermined by interpreting the syntax elements corresponding to thewrap-around padding process with a clipping process.
 16. The computersystem of claim 15, wherein a fractional pixel is interpolated for themotion compensated prediction based on the determined pixel position.17. The computer system of claim 16, wherein an overwrapped region isblended to remove a seam artifact as a post processing.
 18. The computersystem of claim 12, wherein the wrap-around padding process is appliedat a tile or a tile group boundary.
 19. The computer system of claim 12,wherein the at least one coded current picture is a reference for motioncompensation.
 20. A non-transitory computer readable medium havingstored thereon a computer program for video coding, the computer programconfigured to cause one or more computer processors to: decode codedsyntax elements corresponding to a wrap-around padding process based onshifting a reference block by a reference wrap-around padding widthvalue that is determined based on locations of luma samples in thereference block; and reconstruct at least one coded current pictureusing the wrap-around padding process, wherein the wrap-around paddingprocess is applied at boundaries of subpictures.